Treatment of potash ores



United States Patent TREATMENT OF POTASH ORES' N 0 Drawing. Application May 22, .9 53,- Serial N0. 356,878

Claims. (Cl. 209-166) This invention relates to froth flotation of potash ores,

and more particularly to the treatment of clay and otherv slimes occurring in the ore, to enable the flotation and separation to be made economically.

Froth flotation separation of the minerals of potash ores has been known and used commercially for years. In the processes, flotation of potassium chloride (sylvite, and the like) from the other ore constituents may be carried out with certain reagents, also the sodium chloride (halite, and the like)" and other gangue may be floated leaving potassium chloride as the underflow product.

In the flotation of potassium chloride, aliphatic primary amines have been used to float potassium chloride from the ores, but clay and fine slime material in the ore tend to-absorb'thereagent and make the process uneconomical. Various means have beendescribed to overcome this effect such as desliming the ore, or using auxiliary agents such. as starch, dextrins, modifiedv celluloses, etc.

According to, the present invention; we have discovered thatthe clay and slimes of potash oresare'rendered inactive toward aliphatic amine reagent by precipitating certain: metal hydroxides in the brine:

It is an object of the inventionto providev a'process for froth flotation of potassium chloride from potash ores using aliphatic amine reagents.

It is another object of the invention to provide an economical process of froth flotation of potassium chloride from potash ore using an aliphatic amine reagent.

it is still another object of the present invention toprovide a process for the froth flotation of'potassium chloride:

from potash ores with or without the use of organic auxiliary reagents.

It is a further object of the present invention to render inactive the clay and slimes in potash: oresduring the:

froth flotation of potassium chloride from the ores.

In one aspect of the invention magnesium is'pre'cipitated in the brine of a potash flotation pulp as magnesium hydroxide to inactivate the clay and the slime'materialin the ore and prevent reagent absorption. Potashores generally, and particularly ores of the Carlsbad, New Mexico area contain magnesium salts-in varyingamounts; The magnesium content in the ore maybe of'sufficient' quantity to maintain the magnesium level'in the brine for precipitating magnesium hydroxide to-inactivate the elay'an'd slime material, however, soluble salts'of magnesium may be added to maintain the concentration at a sufllcient value. The'magnesium is precipitated as magnesium hydroxide by the addition of caustic soda, lime or other source of hydroxide. The precipitation of magnesium hydroxide is carried out at relatively'low pH values, somewhere around 85. The amount of precipitated magnesium hydroxide in the brine of the-flotation pulp should be enough to coat' or collect the clay and other slimes rendering them inactive toward the, amineflotation' reagent. By thisproeedure the slimes are somewhat dispersed'and' remain suspended in the brine: The concern tr'atesor floated product is relatively'free' fromtlieslime, and similarly thehalite residues tend tosettl'eto a clean 2,757,796 Patented Aug. 7,, 1 9 5.6

ice

product and the magnesium hydoxide floc including the' slimes tends to formand. settle more slowly. Following the flotation more rapid flocculation andv settling of. the slimes can be secured by a change inthe alkalinity of the brine. In the foregoing.description,.reference is made to the hydroxide addition and to alkaline brines, or pulps, and it should be understood that the alkalinity of the pulp is suflicient' to exert a cleansing or scouring effect on' the slimes and clays adheringto the soluble constituents, and this contributes to the Segregation of the substantially clean products noted above. An. alkaline pulp, as used in this specification, is intended to include pulps of both low and high alkalinity.

Potash ores containing magnesium salts tend to be slightly acidic in character, and this natural acidity can be used after flotation in a recirculation pattern to counteractv the alkalinity of the added. hydroxide. Such re.- circulations must be determined by the process in use, and are not considered as an essential feature of this inven-r tion. In commercial. proceduresthe brine is recirculated and the amount of hydroxide required will be reduced over'thatof batch flotation tests.

We have also discovered that other metal hydroxides exert; a similar effect to that of the magnesium hydroxide in:rendering the clay and slimesrinactivetoward the amine reagent.v Alum or aluminum. sulphate may be added in small. quantities tozthe brine and the-precipitation of alwminum hydroxide protects the clay in the same manner asthe magnesium hydroxide. Likewiseferric salts-such as ferric chloride also hydrolyze to ferricrhydrox-ide: and protect the clay and: the slime. Whilealuminum sulphate and ferric chloride hydrolyze in the'brine solution; the effectiveness of= these materials may be changed by altering, the pH of the flotation brine;

Inthe'practiceof this invention'itmay be desirable to remove some of the clayand' slimes'by various: methods of desliming before the addition of'the reagent hydroxide. This can be done by the use of classifiers, hydroseparators, centrifugal cones or other devices for classification. This separation may be carried out at any stage of the process.

The addition of metal hydroxides in to'= a mechanical desliming operation aids in the separation of slime, and the removed slimes can be flocculated and settled by ad justment of the alkalinity. In theremoval of slime, the, addition of a hydroxide to a pH of about 8.5 greatly improves the operation. The clay and'slimes remained dispersed so that effective removal of the solid matter may be secured with lower brine rates and the loss of fine ore slimes with the clay is greatly. reduced. With mechanical methods of slime removal'it is diflicult to remove all'the clay and it maybe necessary'to use the hydroxide coating on'the slime remaining in the brine of the flotation process.

To illustrate the invention a number of tests. are described below. In these tests a batch flotation cell with a capacity ofZOO grams'of oreata' pulp density of. about 30% was used. Brine was added to maintain the level'in the cell during the flotation process. The. ore used in the tests, from the ('Iarlsbad area, comprised potassium chloride, halite, clay andother saltsincluding magnesium salts, was dry groundand'screen'ed to pass a 28 mesh screen; The ore grade was about. 40% potassium chloride. Ore brine (made from ore dissolved in water to thesaturation' point of potassium and sodium chlorides and adjusted to magnesium content) was added to the dry. ore, and the slurry was agitated to wet the ore and scrub the surfaces to release the clayv and other slimes. In, the tests when thehydroxide reagents were used, they were added at this point to allow the precipitation of metal hydroxides to occuriin' contact with elay and other slimes; Mixing for two minutes conditioned the ore. Frothenand' amine" reagents were then added and the flotation continued until complete, generally about minutes. In some tests the floated matter or froth product was fed to a second flotation step, a cleaning stage in which generally no additional reagents were added. A residue of this second flotation is called middlings since it will be returned for retreatment at the first step in a commercial operation.

In the tests described in Table 1 the flotation reagent was octadecylarnine acetate and the frother was one drop the pH required will vary according to the concentration of magnesium in the brine. The amount of magnesium in the brine will determine whether or not suflicient magnesium hydroxide will be formed to produce an effectlve protection from the slime. Accordingly brines which have a magnesium content of less than about 1 gram per liter will produce little or no protection of the clay and slimes. At the higher magnesium content in the brine a marked effect is shown by the reduction of the amount of methylisobutylcarbinol. 10 of amine reagent needed. In another test similar to No.

Table 1 Magnesl Rate Amine Percent Percent Percent Notes on Test No. in Brine, Hydroxide Source in Rate, By KC] 1 special grams/liter lbs/ton lbs/ton weight in in roiloatcd cone. tails cedures 0. 65 32 9. 2 85. 3 35.0 0.65 .32 12.8 92.7 31.3 7.98 .32 10. 5 85. 4 31.7 9.11 32 15. 6 92. 3 29. 2 7. 98 32 32.0 92. 9 13. 6 7. 98 32 32. 5 92. 5 13. 9 19. 76 lime 5 32 38. 1 91. 5 6. 1 O. 65 aluminum sulphate 1 32 22. 6 93. 4 22. 6 0.65 ferric chloride l 32 19. 9 92. 5 25. 5

In the first seven tests magnesium hydroxide was the metal hydroxide used to inactivate the clay and slimes. It is noted that the effect of the hydroxide addition was slight at low magnesium content of the brine. Also, the effect was slight when no hydroxide was added. Where aluminum sulphate and ferric chloride were added there was a reduction in the tailings even at the low magnesium content. The aluminum sulphate and ferric chloride hydrolyze to precipitate aluminum hydroxide and ferric hydroxide respectively.

In the test shown in Table 2 the individual flotations were conditioned 5 minutes. In this series the floated product was refloated in a cleaning step to produce the concentrate and middlings. In Test 12 deslirning by elutriation was also carried out. The flotation reagent and frother were the same as in Table 1, except that 2 drops of frother was used.

ll), where the amount of lime addition and the magnesium concentration were the same, the lime was added to the brine prior to the ore addition. Ore was then added and the flotation carried out. The final results were substantially the same as the results of test No. 10.

Precipitation of metallic hydroxides in the potash ore brine slurry tends to reduce the amount of amine reagent. With metallic hydroxide present in the brine, and using the usual amount of amine, the weight of potassium chloride floated is sharply increased and the percentage of potassium chloride in the tailings is reduced.

In compliance with the law, we have illustrated our invention by specific examples, but there is no intention to limit the invention to the precise details so disclosed except insofar as defined by the appended claims.

Table 2 Magnesium Hydrox- Rate Amine Percent PerccntKClln- Test N0. inBrine, ide in Rate, By Notesonspecial grams/liter Source lbs/ton lbs/ton Weight procedures floated Cone. Midds. Tails.

7.83 lime 5 .32 41.0 96.3 77.7 4.9 7.83 ...do 5 .44 42.1 96.7 70.8 1.5 llbjtonadditionallimo added in cleaning. 6.82 do... 2.5 .32 42.1 97.4 57.5 1.8 2.5 lbs/ton lime prior to desliming and 11b. in cleaning in addition to that reported.

The desliming with the lime was very effective since We claim:

the amount of the amine reagent was reduced. A much smaller amount of lime was then needed in the flotation step for excellent flotation.

The dispersing action of the hydroxide was measured by noting the distribution of water insoluble matter in the slimes, concentrate and tailings of a typical test. In Test 12 38.6% of the water insoluble matter appeared in the removed slimes. In a test using the same elutriation rate for desliming but without added hydroxide, only 5.1% of the water insoluble matter appeared in the removed slimes. In another test the tailings were allowed to settle briefly and the brine decanted oif. The brine carried most of the insoluble matter. In another test on adjusting the pH of the elutriated slimes to 7.00 the slimes flocculated and settled rapidly. In another test the tailings pulp was adjusted to 7.0 pH and good flocculation and settling of the slimes occurred.

The precipitation of magnesium hydroxide is carried out at about pH 8.5 when the magnesium concentration is about 8 grams per liter. The pH range may be from 8 to 9.5. In the precipitation of magnesium hydroxide 1. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes which absorb the amine reagent, the improvement which comprises precipitating a metal hydroxide in the brine of a flotation pulp prior to the introduction of the amine reagent therein to coat and thereby inactivate the clay and slimes from absorbing the amine reagent and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

2. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes which absorb the amine reagent, the improvement which comprises precipitating magnesium hydroxide in the brine of a flotation pulp prior to the introduction of the amine reagent therein to coat and thereby inactivate the clay and slimes from absorbing the amine reagent and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

3. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes which absorb the amine reagent, the improvement which comprises precipitating aluminum hydroxide in the brine of a flotation pulp prior to the introduction of the amine reagent therein to coat and thereby inactivate the clay and slimes from absorbing the amine reagent, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

4. In the alphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes which absorb the amine reagent, the improvement which comprises precipitating ferric hydroxide in the brine of a flotation pulp prior to the introduction of the amine reagent therein to coat and thereby inactivate the clay and slimes from absorbing the amine reagent, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

5. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes which absorb the amine reagent and which ores contains magnesium salts, the improvement which comprises adding a hydroxide material to the brine of a flotation pulp to precipitate magnesium hydroxide in said brine to coat and thereby inactivate the clay and slimes from absorbing the amine reagent, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

6. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes and which contain magnesium salts, the improvement which comprises adding a soluble magnesium salt and a hydroxide material to raise the brine pH to about 8.5 forming suflicient magnesium hydroxide to coat and thereby inactivate the clay and slime from absorbing said amine reagent, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

7. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes and which contain magnesium salts, the improvement which comprises adding a soluble salt of magnesium to raise the magnesium content of the brine to above about 1 gram per liter and adding lime to raise the brine pH to about 8.5 whereby suflicient magnesium hydroxide is formed with said lime to coat and substantially inactivate the clay and slime from absorbing the amine reagent, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

8. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes, the improvement which comprises adding to the brine an aluminum salt hydrolyzable therein to form aluminum hydroxide to coat and thereby inactivate the clay and slimes from absorbing the amine reagents, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

9. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slime, the improvement which comprises adding to the brine a ferric salt hydrolyzable therein to form ferric hydroxide to coat and thereby inactivate the clay and slimes from absorbing the amine reagent, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

10. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes, the improvement which comprises adding alkaline material to the brine of the potash ores to cause the precipitation of metallic hydroxides from soluble metal salts to coat and thereby inactivate the clay and slimes from absorbing the amine reagent, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

11. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes detrimental to the flotation step, the improvement which comprises adding hydroxide material to increase the pH of the brine of the potash ore to precipitate a metal hydroxide in the brine to coat and thereby inactivate the clay and slimes from absorbing said amine reagent, and to maintain said coated clay and slime substantially dispersed and suspended in said brine.

12. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes detrimental to the flotation process; the improvement which comprises desliming a pulp of said potash ore in a saturated brine of the soluble constituents of said ore in the presence of magnesium hydroxide, precipitated in the brine to coat said clay and slime and thereby maintain the same dispersed in the brine and separated from said ore, said desliming being performed prior to the flotation step.

13. In the aliphatic amine reagent flotation of potassium chloride from potash ores containing clay and slimes detrimental to the flotation process and containing soluble metal salts capable of forming insoluble hydroxides, the improvement which comprises adding hydroxide material to increase the pH of the brine of a pulp of the potash ore to precipitate a metal hydroxide in the pulp to coat and thereby inactivate the clay and slimes from absorbing the amine reagents, precipitated in the brine to coat said clay and slime and thereby maintain the same dispersed in the brine and separated from said ore.

14. In the aliphatic amine flotation of potassium chloride from potash ore containing clay and slime, the steps of precipitating a metal hydroxide to coat and thereby protect the clay and slimes from absorbing the amine reagent prior to the flotation step, and then increasing the alkalinity of the system following the flotation step to precipitate additional metal hydroxide to cause a rapid flocculation and settling of the remaining clay and slimes in the clarification of brine for reuse.

15. The process of treating sylvinite ores which comprises forming a sylvinite ore pulp, having a substantial clay and slimes content, precipitating a metal hydroxide as a coating on the surfaces of said clay and slime constituents in the pulp in an action in which adhering slimes and clays are physically separated from the soluble constituents of the pulp and the clay and slime content is maintained dispersed and suspended in the pulp, removing a substantial portion of said coated clay and slime content prior to the introduction of an amine collector reagent into the pulp, and subjecting said pulp, after such desliming step, to the action of an amine collector reagent in an aerating stage for the separation of a sylvite concentrate from the pulp.

References Cited in the file of this patent UNITED STATES PATENTS 2,569,672 Jackson Oct. 2, 1951 FOREIGN PATENTS 195,113 Great Britain Mar. 29, 1923 

1. IN THE ALIPHATIC AMINE REAGENT FLOTATION OF POTASSIUM CHLORIDE FROM POTASH ORES CONTAINING CLAY AND SLIMES WHICH ABSORB THE AMINE REAGENT, THE IMPROVEMENT WHICH COMPRISES PRECIPITATING A METAL HYDROXIDE IN THE BRINE OF A FLOTATION PULP PRIOR TO THE INTRODUCTION OF THE AMINE REAGENT THEREIN TO COAT AND THEREBY INACTIVATE THE CLAY AND SLIMES FROM ABSORBING THE AMINE REAGENT AND TO MAINTAIN SAID COATED CLAY AND SLIME SUBSTANTIALLY DISPERSED AND SUSPENDED IN SAID BRINE. 